Exploring Solar Structure: Facts & Concepts

1. Warm Up 6/3/08 • A refracting telescope produces an image using a(n) ____. a. spectroscope c. mirror b. prism d. objective lens • A reflecting telescope produces an image using a(n) ____. a. lens c. prism b. antenna d. concave mirror • Which property of an optical telescope is associated with sharper images? a. light-gathering power c. magnifying power b. resolving power d. chromatic aberration Answers: 1) d. 2) d. 3) b.

2. The Sun Chapter 24, Section 3

3. Sun Facts • An “Average” Star • Diameter = 109 x Earth • Volume = 1.25 x Earth • Mass = 332,000 x Earth • Density = ¼ x Earth

4. Structure of the Sun • The sun is made of gas, no sharp boundaries exist • We can divide the sun into four parts: the solar interior; the visible surface, or photosphere; and two atmospheric layers, the chromosphere and corona • The interior makes up all but a tiny fraction of the sun’s mass

5. Solar Structure

6. Concept Check • What is the structure of the sun? • The solar interior, the photosphere, the chromosphere, and the corona

7. Photosphere • Photosphere – radiates most of the light we see and can be thought of as the visible “surface” of the sun • The photosphere consists of a layer of gas less than 500 km thick • It has a grainy texture resulting from numerous relatively small (the size of Texas), bright markings called granules • They owe their brightness to hotter gases rising from the interior, it spreads and cools, eventually sinking back into the interior • The combined motion of the hotter material replacing the cooler material is called convection

8. Photosphere

9. Chromosphere • Chromosphere – A relatively thin layer of hot gases a few km thick above the photosphere • Only observable for a few moments during a total solar eclipse or with special instruments that block out the light from the photosphere

10. Chromosphere

11. Corona and Solar Wind • Corona – outer most portion of the solar atmosphere, very weak and is visible only when the photosphere is covered • Envelope of ionized gases normally extend millions of kilometers from the sun • Solar Wind – Streams of protons and electrons that boil from the corona • The wind travels outward through the solar system at speeds up to 800 km/s • During this journey, the solar wind interacts with different bodies in the solar system, including our Earth’s magnetosphere

12. Corona and Solar Wind

13. Concept Check • Which layer of the sun can be thought of as its surface? • The photosphere

14. Sunspots • Sunspots – dark regions on the surface of the photosphere, an individual spot contains a black center rimmed by a lighter region • Sunspots appear dark because of their temperature, about 1500 K less than that of the surrounding solar surface • During the 1800s, people believed that a tiny planet named Vulcan was orbiting between Mercury and the Sun • The number of sunspots varies on an 11-year cycle

15. Sunspots

16. Mean Annual Sunspot Numbers

17. Concept Check • Are the same number of sunspots always present on the sun? Explain. • No, because the number of sunspots varies in an 11-year cycle.

18. Prominences • Prominences – huge cloudlike structures consisting of chromospheric gases • They appear as great arches that extend into the corona • Others rise explosively away from the sun • Prominences are ionized gases trapped by magnetic fields that extend from regions of intense solar activity

19. Prominences

20. Solar Flares • Solar Flares – brief outbursts that normally last about an hour and appear as a sudden brightening of the region above a sunspot cluster • During their existence, solar flares release enormous amounts of energy, much of it in the form of ultraviolet, radio, and x-ray radiation • Fast moving particles are ejected, causing the solar wind to intensify • Auroras – following solar flares, Earth’s upper atmosphere near the magnetic poles is set alight; also called the northern and southern lights

21. Solar Flares and the Aurora

22. The Solar Interior • Nuclear Fusion – The process by which the sun produces energy; this nuclear reaction converts four hydrogen nuclei into the nucleus of a helium atom and tremendous energy is released • Only a small percentage of the hydrogen in the nuclear reaction is actually converted to energy • As Hydrogen is consumed, the product of the reaction – helium – forms the solar core • It is believed that a star our size can exist in its stable state for ~10 Billion years, making our sun middle-aged at ~4.5 Billion years old

23. Nuclear Fusion

24. Concept Check • How does the sun produce energy? • Deep in its interior, the sun produces energy by a process known as nuclear fusion, wherein four hydrogen nuclei are converted into the nucleus of a helium atom and tremendous energy is released.

25. Assignment • Read Chapter 24, Section 3 (pg. 684-690) • Do Chapter 24 Assessment #1-34 (pg. 695-696) • Study for the Chapter 24 Quiz!!!